1. Technical Field
The present invention relates to a print control device that controls a printing unit in a printing apparatus, to a printing apparatus and to a method of providing information in a printing apparatus.
2. Related Art
For example, a printing apparatus that is equipped with a plurality of recording heads that eject ink (fluid ejecting units) is disclosed in JP-A-2004-25551. In this printing apparatus, a plurality of print heads and a plurality of driving control units that control driving of the plurality of print heads are mounted on a carriage provided so as to be capable of reciprocating. Furthermore, a plurality of data processing units that transfer data to the individual driving control units are mounted in the main body of the printing apparatus. A plurality of circuit sets each consisting of one driving control unit and one data processing unit are connected to every predetermined number of print heads in a main control unit that controls reciprocation of the carriage. With this printing apparatus, since a configuration is adopted in which every predetermined number of print heads is provided with one of a plurality of circuit sets, the processing load on each data processing unit is reduced.
Furthermore, in the case where there are a large number of print heads, it has been thought that it would be effective to adopt a printing apparatus configuration in which two or more main control units are provided and a print control device, in which a main control unit, a data processing unit and a driving control unit form a circuit set, is formed on a single substrate. This substrate is then provided in a plurality. With this configuration, since a large number of recording heads are allocated to and controlled by a plurality of print control devices, as the number of recording heads increases, the number of print control devices also increases, whereby the load on each print control device remains relatively small and the required print processing speed can be ensured.
In this case, various control commands, such as a carriage initiating command, which is to be output at a stage when all the preparation for starting recording with a plurality of recording heads that the individual print control devices are in charge of has been performed, and a transport command, which is to be output to initiate transport of a recording medium once recording has finished, are individually managed by the print control devices. Consequently, it is necessary that the timings at which these control commands are output be synchronized between the two or more print control devices. For example, one print control device is made the master (master-side print control device) and another print control device is made the slave (slave-side print control device). A configuration is adopted in which, at a stage when a command to be output by the master-side print control device and a command to be output by the slave-side print control device are both present, the individual print control devices transmit these commands to the driving control unit (mechanical controller or the like) of the carriage system and the transport system in synchronization with each other. With such a configuration, it becomes possible to control ink ejection processing for individual recording heads, which are respectively controlled by the print control devices, and transport processing for a printing medium controlled by a driving control unit to be at suitable timings.
In addition to a plurality of recording heads being allocated to a plurality of print control devices, it is preferable that components included in the printing apparatus in a plurality, such as a plurality of ink cartridges that supply ink to the recording heads and nozzle testing devices that test for clogging of the nozzles of the recording heads, be allocated to and connected to a plurality of print control devices and that their loads be allocated among the individual print control devices. Here, typically, memory elements, into which ink-related information such as information on the amounts of ink remaining and the colors of ink has been written, are provided in ink cartridges and the individual print control devices are allocated with and manage the ink-related information such as the amount of ink remaining for each ink by accessing the memory elements of the ink cartridges they are in charge of.
Furthermore, in this type of printing apparatus, there are cases where a host control unit acquires state (status) information regarding a driving control device via the individual print control devices and issues instructions in accordance with the states at that time. In such a case, the host control unit transmits an information acquisition command to a print control device and the print control device then transmits the received information acquisition command to the driving control device. Then, the print control device transmits information transmitted from the driving control device as a response to the host control unit.
Sometimes cases occur in which a command (internal command) is individually generated in only a certain print control device among a plurality of print control devices. For example, an error in a component such as a recording head, ink cartridge, nozzle testing device or the like that the print control device is in charge of such as an out of ink error (end of ink error) or a clogged nozzle error for a nozzle testing device in an ink cartridge that a print control device is in charge of, are examples of internal commands generated just within the certain print control device.
For example, when an internal command is generated by a master-side print control device, an internal command is not generated by the other slave-side print control device. Consequently, there is a problem in that when synchronization needs to be attained in order for the master-side print control device to output an internal command, since the command is not present in the slave-side print control device, the internal command cannot be output. For example, if a configuration is adopted in which a plurality of print control devices are connected to one another through communication lines and internal commands are also transferred from one print control device to the other print control devices, in the synchronization processing, since a certain internal command is present in all the individual print control devices, the internal command is then able to be output. Typically, a print control device includes a queue in which commands are stored in the order in which they were obtained and the commands are output in the order in which they are stored in the queue.
In the case where an internal command is transmitted by communication though a communication line between a plurality of print control devices, the internal command arrives at the print control device that is to be the recipient of the internal command after an amount of time necessary to perform the communication (communication time) from the time at which the command was generated in print control device that was the sender of the internal command. For example, after an internal command has been generated by one print control device, if each of the print control devices receives a state information acquisition command from the host control unit during the time up until the internal command arrives at the other print control device, the orders in which the commands are stored in the queues in the respective print control devices will become different. As a result, in the synchronization processing, there will be a problem in that the respective commands to be output from the print control devices will not match and a command transmission error will be generated.
Furthermore, internal commands may include commands for detecting the states of devices or the states of components such as ink cartridges or the like and for making notification of an OK state or an NG state in response to a detection result in order to cause the printing apparatus to perform a predetermined operation such as when initiating the printing apparatus or when an ink cartridge is to be replaced. In such a case, when the state is the OK state, an OK state command (normal state command) is issued and when the state is the NG state, an NG state command (abnormal state command) is issued. In the case where the expiration date of an ink cartridge has passed, printing can be performed using the ink cartridge as is even though it is not optimal. Consequently, in the case where an NG state is detected because the expiration date has passed, an NG state command is transmitted to the host control unit, the host control unit prompts the user to select whether to use the non-optimal component as is or to replace the non-optimal component with a satisfactory component, and when an input is made to use the ink cartridge as is, the error is cleared and an OK state command is issued.
In such a case, when one printing control device has an OK state and another print control device has an NG state, when the print control devices receive an information acquisition command from the host control unit in the period up until the other print control device receives an OK state command once the error has been cleared, the orders in which commands are stored in the queues in the respective print control devices will become different. Of course, in addition to this reason, there are various other reasons why the orders in which commands are stored in the queues may become different.
Thus, if a configuration is adopted in which the individual print control devices transmit an information acquisition command received from the host control unit to the driving control device and transmit state information acquired from the driving control device to the host control unit as a response to the information acquisition command, the frequency with which the orders in which the commands are stored in the queues become different in the individual print control devices will be high. For such a case, adding error avoidance processing (an error avoiding unit) to the synchronization processing as a countermeasure to avoid generation of errors in cases where the orders in which the commands are stored in queues have become different has been considered. However, if a configuration is adopted in which information acquisition commands are stored in queues, the frequency with which error avoidance processing is executed will increase and when the error avoidance processing is executed, the frequency with which the orders in which commands are stored in the queues in the print control devices become different due to the information acquisition commands will increase and therefore there is a concern that a problem will occur in that for example command output processing will not progress smoothly.